It is sometimes the case that soil properties at a construction site are not sufficiently stable to allow a structure to be built. Further, currently built structures sometimes become cracked, experience partial collapse, or are otherwise damaged due to unstable soil conditions beneath the structure. Anchor assemblies are used in order to provide structural support to building foundations, retaining walls, oil and gas pipelines, utility towers, and other structures in both new and current construction. Anchor assemblies include a shaft that carries one or more bearing plates that are generally arranged in a helical configuration thereon. Powered rotation is communicated to the shaft to screw the anchor assembly into the ground. Once inserted, the building or other structure may be built or repaired as some or all of its weight is then carried by the anchor assembly.
The bearing capacity of an anchor assembly is a function of the torque placed upon the anchor assembly during insertion and a property of the soil sometimes known as the soil value blow count. Bearing capacity of the anchor assembly can be increased upon increasing the diameter of the bearing plates. In this regard, increasing the diameter of the bearing plates increases the amount of torque necessary to drive the anchor assembly into the ground. Additionally, the bearing plates may be driven deeper into the ground in order to reach soil having a greater density to increase the bearing capacity of the anchor assembly. It is sometimes the case that undesirable friction is created between the bearing plate and the ground when driving the anchor assembly therein. A sharp angle at the tip of the leading edge of the bearing plate may act to generate this friction. Frictional forces act to make it harder to drive the bearing plates into the ground and therefore require that a greater torque be imparted onto the anchor assembly. As the bearing capacity of the anchor assembly is calculated by measuring the required torque, this value may be skewed upon the presence of friction on the bearing plates during installation.
It is also the case that present installation equipment may be capable of generating torque greater than the maximum structural torsional load capacity of the anchor assembly. The bearing plate may possibly hit a rock or other obstruction during insertion that causes one or more components of the anchor assembly to break. In this regard, attempts have been made to strengthen the anchor assembly by heat treating the shaft and/or bearing plates. Additional solutions involve making these components out of a stronger material. Unfortunately, these options are often expensive and time consuming.
A geological survey of the construction site is often conducted in order to ascertain properties of the soil onto which the structure is built. From this data, an anchor assembly having appropriately sized and spaced bearing plates may be selected in order to achieve a desired bearing capacity. Unfortunately, it is sometimes the case that during insertion of the anchor assembly it is discovered that a different anchor assembly is needed. For example, the soil properties from one end of the construction site to the other may vary. The geologist may have tested the soil at a different location than where the anchor assembly is inserted thus resulting in a different soil density at the location of insertion. Additionally, other circumstances arise which prevent the use of an initially chosen anchor assembly. In these instances a different anchor assembly must be used in order to achieve a desired bearing capacity. As bearing plates are generally welded onto shafts, the installer must travel with and keep a variety of differently sized and configured anchor assemblies in order to account for such possibilities. As such, there remains room for variation and improvement within the art.